I like Ainsley I dont think of anus either. But kids might make the connection.
If your worried about Charlotte being too popular, as an alternate I think Scarlett sounds very similar yet not as popular (atleast where im from)

I would go with BrennaCharlotte. I know what you mean by picturing a second daughter named Brenna, but you may have boys in future pregnancies. If it were me, I would regret not using a name I loved to "save" it for a future child.

My vote goes for Brenna. If you love it so much (understandably so; it's lovely), I think you should go for it, especially since you may not have another daughter to "save" it for (even if you have ten future kids, they might all be boys). Charlotte is a beautiful name, but it's skyrocketing in popularity - as others have said, BrennaCharlotte is a lovely way of using both names. Ainsley doesn't do anything for me personally.

Charlotte is my fav, as it is quite timeless. However, it's popularity is a huge strike against it. Brenna would be my #2, but I'm not really a big fan. To me, it lacks the timeless quality that Charlotte has.

INTJ Anthropologist Living in the centre of China, married to a Persian, and just enjoying a completely unpredictable life